Stabilized herbicidal composition

ABSTRACT

A herbicide composition includes a fenoxaprop ester and a weak acid buffer system. The buffer system maintains the herbicidal composition at a pH in the range of 4 to 8. In one non-limiting embodiment, the fenoxaprop ester is fenoxaprop ethyl. The buffer system can include an amine-containing material, such as a tertiary amine. The herbicide composition can include other herbicides, such as weak acid herbicides, for example pyrasulfotole, bromoxynil, and/or bromoxynil esters and can include one or more safeners.

This application is a divisional application of U.S. patent applicationSer. No. 11/509,283, filed Aug. 24, 2006, currently pending, which is acontinuation-in-part of U.S. application Ser. No. 11/295,757, filed Dec.6, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to crop protection compositionsand, in one embodiment, to crop protection compositions containingaryloxyphenoxypropionic esters and uses thereof.

2. Description of the Current Technology

A wide variety of herbicides are in use today. These known herbicidescan be effective against different types of undesirable vegetation andcan act in different ways. For example, some herbicides are particularlyuseful when applied to broad leaf plants while others are more usefulwhen applied to grassy plants. Also, these different herbicides canperform their herbicidal function in different ways. For example, someherbicides may act as acetyl-CoA carboxylase inhibitors while others actin a completely different manner, such as acetolactate synthaseinhibitors, or carotenoid biosynthesis inhibitors, or mitosisinhibitors, or photosynthesis inhibitors, just to name a few. In orderto combat a wide variety of different types of undesirable vegetation,it is not uncommon to combine several different types of herbicides intoa single herbicidal composition. This herbicidal composition can then beapplied to a field in a single application without having to apply eachof the herbicides individually.

An example of one particularly useful group of herbicides arearyloxyphenoxypropionic esters. Aryloxyphenoxypropionic esters typicallyact as acetyl-CoA carboxylase inhibitors. An example of such herbicidesinclude fenoxaprop esters, such as fenoxaprop ethyl, commerciallyavailable from Bayer CropScience, LP. The fenoxaprop esters, such asfenoxaprop ethyl, are particularly useful for application to cerealcrops to combat grassy weeds. A basic formula for fenoxaprop herbicidesis shown in Formula I below.

The fenoxaprop ester herbicides are quite well adapted for applicationto cereal crops and have found widespread acceptance. However, it hasbeen observed that when a fenoxaprop ester herbicide, particularlyfenoxaprop ethyl or a fenoxaprop lower alkyl ester, is mixed withcertain other herbicides, the fenoxaprop ester herbicide can degrademore rapidly that if the fenoxaprop herbicide were not mixed with theother herbicides. This has been particularly observed when a fenoxapropester is mixed with herbicides that act as weak acids, such aspyrasulfotole and bromoxynil. This increased degradation of fenoxapropesters can be disadvantageous to a farmer because it can decrease theuseful shelf life of a fenoxaprop ester containing herbicidalcomposition. See FIG. 1 for example.

Therefore, it would be useful to provide a fenoxaprop ester containingherbicidal composition that reduces or eliminates the drawbacksassociated with previous herbicidal compositions.

SUMMARY OF THE INVENTION

A herbicide composition comprises a fenoxaprop ester and a buffersystem. The buffer system maintains the herbicidal composition at a pHin the range of 4 to 8, such as 4.5 to 8, such as 5 to 7.5, such as 5.8to 7.5. In one non-limiting embodiment, the fenoxaprop ester isfenoxaprop ethyl. The buffer system can comprise an amine-containingmaterial, such as a tertiary amine. The herbicide composition caninclude other herbicides, such as weak acid herbicides, and can includeone or more safeners.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of the acid-catalyzed hydrolysisand transesterification reaction mechanism of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As used herein, all numbers, such as but not limited to dimensions,physical characteristics, processing parameters, quantities ofingredients, reaction conditions, and the like, used in thespecification and claims are to be understood as being modified in allinstances by the term “about”. Accordingly, unless indicated to thecontrary, the numerical values set forth in the following specificationand claims may vary depending upon the desired properties sought to beobtained by the present invention. At the very least, and not as anattempt to limit the application of the doctrine of equivalents to thescope of the claims, each numerical value should at least be construedin light of the number of reported significant digits and by applyingordinary rounding techniques. Moreover, all ranges disclosed herein areto be understood to encompass the beginning and ending range values andany and all subranges subsumed therein. For example, a stated range of“1 to 10” should be considered to include any and all subranges between(and inclusive of) the minimum value of 1 and the maximum value of 10;that is, all subranges beginning with a minimum value of 1 or more andending with a maximum value of 10 or less, e.g., 1 to 3.5, 5.5 to 10,2.3 to 7.3, etc. All references and publications referred to herein,such as but not limited to U.S. patents and published applications, areto be understood as being herein incorporated by reference in theirentirety.

In one non-limiting embodiment, a herbicidal composition of theinvention comprises a aryloxyphenoxypropionic ester, such as afenoxaprop ester herbicide (optically active or racemic mixture), abuffer system, optionally one or more weak acid herbicides, andoptionally one or more safeners.

Aryloxyphenoxypropionic esters have been described above. Non-limitingexamples of aryloxyphenoxypropionic esters are described, for example,in U.S. Pat. Nos. 6,908,883 B2 and 6,887,827 B2. The present inventionwill be described with respect to the use of a fenoxaprop ester, such asfenoxaprop ethyl, in a herbicide composition. However, it is to beunderstood that the invention is not limited to use with fenoxapropethyl but is believed to be applicable to other aryloxyphenoxypropionicesters, e.g., fenoxaprop esters.

The buffer system can be a weak acid buffer system and can comprise awater-miscible acid and a water-miscible salt of the acid. In a highlyadvantageous embodiment of the invention, the water-miscible acid is aherbicide. By the term “weak acid” is meant an acid with a pK_(a) in therange of 0.1 to 10 at 25° C. The buffer system is configured to maintainthe pH of the herbicidal composition in the range of 4 to 10, e.g., 4 to8, e.g., 4.5 to 8, e.g., 5 to 7.5, e.g., 5.8 to 7.5. For example, thebuffer system could maintain the pH of the herbicide composition in therange of 4 to 7, such as 5 to 7, such as 5 to 6.

The salt of the weak acid can be an amine or imine salt of the weakacid. Substantially non-nucleophilic conjugate amines are preferred toprepare the amine salts. Tertiary alkyl amines are most preferred,although secondary alkyl amines and primary amines may be used. Theamine can also comprise primary, secondary, and/or tertiary aminefunction in any combination within the same molecule or the mixture ofthem. For example, the amine can be a tertiary amine or a trialkylaminein which the alkyl can be optionally substituted with a hydroxy group.

Generally one or more of the alkyl moieties of the amine has from 1 to50 carbons, preferably from 1 to 10 carbons, and, in an alternativeembodiment, has from 2 to 6 carbons. The alkyl group can be straightchained, branched, or cyclic alkyl. The one or more alkyl moieties canbe, independent of one another, optionally substituted by one or moreether groups, e.g. alkoxy, hydroxyl groups, thiol groups, alkylthio,alkene, alkyne, amino, alkylamino, dialkylamino, or combinations ofthese functional groups that include a carbon to carbon double bond(i.e., an alkene) or carbon to carbon triple bond (i.e., an alkyne). Theamine can be in the form of monoamine or diamine or polyamine. In apreferred embodiment, the one or more alkyl moieties of the amine may behydroxylated, ethoxylated, diethoxylated, triethoxylated, or substitutedwith hydroxyethoxy or hydroxypropoxy groups wherein the number of ethoxyand propoxy groups may be from 1 to 60.

The composition can be in any formulation form, particularly a liquidcomposition, such as an emulsifiable concentrate, suspoemulsion,suspension concentrate, or a solution, such as an aqueous solution. Inone non-limiting embodiment, an emulsifiable concentrate and asuspoemulsion is preferred.

The conjugate base of the amine salt may also serve as a surfactant inthe composition, such as a nonionic surfactant or an ionic surfactant.

Representative conjugate amines and imines include one or more of thefollowing: tertiary amines such as triethanolamine, triisopropanolamine;trialkylamines such as triethylamine, trimethylamine, tripropylamine,triisopropylamine, 1-octaneamine-N,N-dimethyl,N,N-dimethylcyclohexanamine, N,N-dimethyl-1-hexadecylamine,1-dodeccanamine-N,N-dimethyl, ethyldiethanolamine,hexamethylenetetramine, N,N,N″,N″-tetrakis-(2-hydroxypropyl)ethylenediamine, dicocoalkyl-methylamine, didecylmethylamine, tridodecyamine,trihexadecylamine; monoalkyldimethylamines such as dodecyldimethylamine,hexadecyl-dimethylamine, octadecyl-dimethylamine,cocoalkyl-dimethylamine, soyalkyl-dimethylamine,soyaalkyl-dimethylamine, tallowalkyl-dimethylamine, hydrogenatedtallowalkyl-dimethylamine, cottonseed alkyl-dimethylamine; ethoxylatedalkylamines such as ethoxylated (n) cocoalkylamine, ethoxylated (n)tallowalkylamine, ethoxylated (n) soyaalkylamine, ethoxylated cottonseedamine, oleyl amine ethoxylate, ethoxylated (n) octadecylamine, (ethoxygroup numbers n may be from 1 to 60), ethoxylated diamines, such asethoxylated (n) N-tallow-1,3-diaminopropane, ethoxylated (n)N-tallow-1,3-diaminopropane, ethoxylated (n)N-tallow-1,3-diaminopropane,N,N-bis[α-ethyl-ω-hydroxypoly(oxyethylene)alkylamine; thepoly(oxyethylene) content average 3 moles; the alkyl groups (C14-C18)are derived from tallow, or from soybean or cottonseed oil acids, orother crop or vegetable seeds oil acids.N,N-bis(2-hydroxyethyl)alkylamine, where the alkyl groups (C8-C18) arederived from coconut, cottonseed, soya, or tallow acids or other cropsor vegetable seed acids; N,N-Bis2-(ω-hydroxypolyoxyethylene)ethyl)alkylamine; the reaction product of 1mole N,N-bis(2-hydroxyethyl)alkylamine and 3-60 moles of ethylene oxide,where the alkylgroup (C8-C18) is derived from coconut, cottonseed, soya,or tallow acids or other crop or vegetable seed acids.N,N-Bis-2-(ω-hydroxypolyoxyethylene/polyoxypropylene)ethyl alkylamine;the reaction product of 1 mole of N,N-bis(2-hydroxyethyl alkylamine) and3-60 moles of ethylene oxide and propylene oxide, where the alkyl group(C8-C18) is derived from coconut, cottonseed, soya, or tallow acids orother crop seeds or vegetable seeds acids,N,N′-Bis,(2-hydroxyethyl)-C12-C18 alkylamine,N,N′-bis(polyoxyethylene)cetylamine,N,N′-Bis(polyoxyethylene)oleylamine,N,N′-bis(polyoxyethylene)stearylamine,N,N′-dinitropentamethylenetetramine, ethoxylated abietylamine. Secondaryamine such as diethylamine, diisopropanolamine, dimethylamine,ditallowamine, dicocoalkylamine, dehydrogenated tallowalkylamine,didecylamine, dioctadecylamine, ethylethanolamine. Primary amine such asethanolamine, butylamine, ethylamine, oleylamine, isopropylamine,isopropanolamine, propylamine, dodecanamine, primary N-alkylamine, wherethe alkyl group (C8-C18) is derived from coconut, cottonseed, soya ortallow acids, polyoxyethylated primary amine (C14-C18); the fatty amineis derived from an animal source and contains 3% water, thepoly(oxyethylene) content average 20 moles, amines, C14-C15 alkyl,ethoxylated, amines, C16-C18 and C18 unsaturated, alkyl, ethoxylated,amines, tallowalkyl, ethoxylated with polyethylene, triethylenetetramine, ethylendiamine, diethyleneamine, diethylenetriamine,N-oleyl-1,3-propanediamine, tetramethylene pentamine, polypropyleneglycol bis(2-aminopropyl)ether, 2-[(2-aminoethyl)amino]ethanol,2-amino-2-methyl-1-propanol. Imines such asN,N′-disalicylidene-1,2-diaminopropane.

The herbicidal composition can include one or more weak acids.Non-limiting examples of representative weak acids include thefollowing: phenols, phenol esters and mixtures of phenols and phenolesters, substituted phenols, conjugated diketones, conjugatedtriketones, carboxylic acids or their salts, such as alkylcarboxylicacids, phenylcarboxylic acids, phenoxy acetic acids, phenoxy propionicacids and their substituted and branched analogs and ester analogs.

Non-limiting examples of representative weak acids that areagriculturally acceptable herbicides include the following: pyrazoleherbicides such as pyrasulfotole, nitrile herbicides such as bromoxynil,chloroxynil, or ioxynil, or a propesticidal precursor thereof, forexample, bromoxynil octanoate or bromoxynil heptanoate, 2,4-D, Dicamba,MCPA, MCPP(mecoprop), or MCPB.

The herbicide composition may also be an agriculturally acceptablesafener, such as but not limited to mefenpyr, isoxadifen, fenchlorazole,or cloquintocet, just to name a few.

Fenoxaprop ethyl when mixed with a weak acid herbicide (likepyrasulfotole) tends to degrade, e.g., hydrolyze, over time. In order tocombat this degradation, a buffer system in accordance with theinvention is introduced to the composition. An amine-containing buffersystem, such as triethanolamine, triethylamine, and/ortriisopropanolamine, has been found to be particularly useful.

In one non-limiting embodiment, the composition comprises (by weightpercent based on the total weight of the composition) 3 wt. % to 6 wt. %pyrasulfotole, 7 wt. % to 10 wt. % fenoxaprop-ethyl, 1 wt. % to 4 wt. %triethanolamine, and, optionally, 3 wt. % to 6 wt. % mefenpyr. Theremainder of the composition can comprise fillers as are conventional inthe art. The components can be emulsified and/or can be dissolved ordispersed in any conventional solvent.

Example 1

An emulsifiable concentrate of fenoxaprop-ethyl, mefenpyr, andpyrasulfotole was prepared. Triethanolamine was selected as the buffer.The mixture of Table 1 was prepared by mixing the liquid ingredients,then the solid ingredients at 50° C.

TABLE 1 INGREDIENTS Pyrasulfotole (99% pure) Mefenpyr (94.8% pure)fenoxyprop-ethyl (94% pure) ¹alkyl alcohol ethoxylate ²castor oilethoxylated ³benzene sulfonic acid, calcium salt Propylene CarbonateTriethanolamine ⁴aromatic organic solvent ¹Genopol X 060 alkylalcoholethoxylate commercially available from Clariant Corporation. ²EmulsogenEL 400 commercially available from Clariant Corporation.³Phenylsulfonate CA commercially available from Clariant Corporation.⁴A150 commercially available from Exxon Corporation

The mixture was tested for long-term storage stability by subjectingseparate samples to different temperatures for eight weeks. Thefollowing test results were obtained and are shown in Table 2.

TABLE 2 avg. Wt % avg. Wt % avg. Wt % Active ingredient namepyrasulfotole mefenpyr fenoxaprop-ethyl 8 weeks @ 0° C. 5.57 3.77 9.41 8weeks @ room temp. 5.67 3.76 9.34 change from 0° C. 1.71% −0.17% −0.69%8 weeks @ 40° C. 5.53 3.74 9.00 change from 0° C. −0.82% −0.65% −4.31% 8weeks @ 50° C. 5.51 3.72 8.58 change from 0° C. −1.12% −1.17% −8.83%

Comparative Example 2

A mixture of fenoxaprop-ethyl, mefenpyr, pyrasulfotole, and fillers wasprepared in similar manner as in Table 1 but without a buffer system ofthe invention (see Table 3).

TABLE 3 INGREDIENTS Pyrasulfotole (99% pure) Mefenpyr (94.8% pure)Fenoxyprop-ethyl (94% pure) alkyl alcohol ethoxylate ²benzene sulfonicacid calcium salt ³epoxidized soy oil ⁴ethoxylated sulfate PropyleneCarbonate ⁵aromatic organic solvent ¹Genopol X-060 commerciallyavailable from Clariant Corporation. ²Ninate 401A commercially availablefrom Stepan Company. ³Edenol D81/Vikoflex 7170 commercially availablefrom Clariant Corporation. ⁴Soprophor 4D384 commercially available fromRhodia Corporation. ⁵A150 commercially available from Exxon Corporation.

The mixture was tested for long-term storage stability by subjectingseparate samples to different temperatures for eight weeks. Thefollowing test results were obtained and shown in Table 4.

TABLE 4 avg. Wt % avg. Wt % avg. Wt % Active ingredient namepyrasulfotole mefenpyr fenoxaprop-ethyl 8 weeks @ 0° C. 4.76 3.81 8.20 8weeks @ room temp. 4.75 4.01 6.49 change from 0° C. −0.21% +5.24%−20.85% 8 weeks @ 40° C. 4.69 3.85 2.64 change from 0° C. −1.47% −1.05%−67.80% 8 weeks @ 50° C. 4.54 3.97 0.91 change from 0° C. −4.62% −4.20%−88.90%

As can be seen from Table 4, there was a significant drop in theconcentration of fenoxaprop-ethyl without the buffer system of theinvention.

What is claimed is:
 1. A method of improving the stability of an herbicidal composition comprising: a) combining fenoxaprop ethyl with a buffer system consisting essentially of i) triethanolamine; and ii) one or more weak acid herbicides comprising pyrasulfotole to form a stable herbicidal composition, wherein said fenoxaprop ethyl combined with said buffer system has improved stability relative to an herbicidal composition that contains fenoxaprop ethyl and a weak acid herbicide in combination without said triethanolamine, and wherein the improved stability of the fenoxaprop ethyl is quantifiable as a decreased amount of fenoxaprop ethyl degradation, as compared to the amount of degradation observed in fenoxaprop ethyl when combined with a weak acid in the absence of triethanolamine.
 2. The method of claim 1 wherein said herbicidal composition comprises 3 to 6 wt % pyrasulfotole and 7 to 10 wt % fenoxaprop ethyl.
 3. The method of claim 1 wherein said buffer system comprises 1 to 4 wt % triethanolamine.
 4. The method of claim 1, further comprising adding a safener to said composition.
 5. The method of claim 4 wherein said safener is selected from the group consisting of mefenpyr, isoxadifen, fenchlorazole and cloquinocet.
 6. The method of claim 4 wherein said safener comprises 3 to 6 wt % mefenpyr.
 7. The method of claim 1, wherein the herbicidal composition is an emulsion concentrate formulation.
 8. The method of claim 2, wherein the herbicidal composition is an emulsion concentrate formulation.
 9. The method of claim 1, wherein said herbicidal composition further comprises benzene sulfonic acid calcium salt.
 10. The method of claim 1 wherein said herbicidal composition comprises 3 to 6 wt % pyrasulfotole and 7 to 10 wt % fenoxaprop ethyl and 1 to 4 wt % triethanolamine.
 11. The method of claim 1 wherein said herbicidal composition comprises: 3 to 6 wt % pyrasulfotole, 7 to 10 wt % fenoxaprop ethyl; 1 to 4 wt % triethanolamine; and 3 to 6 wt % mefenpyr.
 12. The method of claim 1, wherein said buffer system maintains the herbicidal composition at a pH in the range of 4 to
 8. 13. The method of claim 1, wherein said buffer system maintains the herbicidal composition at a pH in the range of 5 to 7.5.
 14. The method of claim 1, wherein said buffer system maintains the herbicidal composition at a pH in the range of 5.8 to 7.5.
 15. The method of claim 1, wherein the stability of fenoxaprop ethyl in said herbicidal composition is improved after 8 weeks of incubation at 0° C. relative to fenoxaprop ethyl in an herbicidal composition without said buffer system.
 16. The method of claim 1, wherein the stability of fenoxaprop ethyl in said herbicidal composition is improved after 8 weeks of incubation at 40° C. relative to fenoxaprop ethyl in an herbicidal composition without said buffer system.
 17. The method of claim 1, wherein the stability of fenoxaprop ethyl in said herbicidal composition is improved after 8 weeks of incubation at 50° C. relative to fenoxaprop ethyl in an herbicidal composition without said buffer system.
 18. The method of claim 1, wherein the buffer system consists of i) triethanolamine; and ii) one or more weak acid herbicides comprising pyrasulfotole to form a stable herbicidal composition.
 19. A method of improving the stability of an herbicidal composition consisting essentially of: a) combining fenoxaprop ethyl with a buffer system consisting essentially of i) triethanolamine; and ii) one or more weak acid herbicides comprising pyrasulfotole to form a stable herbicidal composition, wherein said fenoxaprop ethyl combined with said buffer system has improved stability relative to an herbicidal composition that contains fenoxaprop ethyl and a weak acid herbicide in combination without said triethanolamine, and wherein the improved stability of the fenoxaprop ethyl is quantifiable as a decreased amount of fenoxaprop ethyl degradation, as compared to the amount of degradation observed in fenoxaprop ethyl when combined with a weak acid in the absence of triethanolamine.
 20. The method of claim 19, wherein the buffer system consists of i) triethanolamine and ii) one or more weak acid herbicides comprising pyrasulfotole to form a stable herbicidal composition. 